JPH107625A - Production of cyclohexylamine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply and safely obtain cyclohexylamine useful as a synthetic intermediate for sweeteners, a treating agent, etc., for boiler water in high conversion and selectivity by hydrogenating aniline in the presence of a specific catalyst at a specific temperature under a specific hydrogen pressure. SOLUTION: (A) Aniline is hydrogenated in the presence of (B) a catalyst of a chromium-modified cobalt boride (e.g. containing chromium in an amount of 2-10wt.% based on weight of cobalt boride) in an amount of >=0.6wt.% based on the component A or a catalyst of thorium modified cobalt boride (e.g. containing thorium in an amount of 2-15wt.% based on weight of cobalt boride) at 150-250 deg.C under 1-20atm hydrogen atmosphere. The component B is prepared by modifying cobalt boride with an organic salt or an inorganic salt of chromium or thorium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel process for hydrogenating aniline to form cyclohexylamine in the presence of a cobalt boride catalyst modified with chromium (Cr) or thorium (Th) as a metal transition element. It is about.

[0002]

2. Description of the Related Art Conventionally, cyclohexylamine has been used in the synthesis of sodium cyclamate (cyclohexylsulfamate) and calcium cyclamate, which are used as artificial sweeteners, and has been used as a treating agent for boiler water, a rubber accelerator and a rust inhibitor. It can also be used for industrial applications. Furthermore, cyclohexylamine is an important synthetic intermediate in industrial chemistry.

[0003] The preparation of cyclohexylamine has hitherto been reported in a large number of documents. Most of these processes hydrogenate aniline in the presence of a catalyst to form cyclohexylamine, but the hydrogenation catalyst used is
Precious metals such as Ru and Pd are mainly selected, and the pressure used is several tens to several hundreds times the atmospheric pressure. This high pressure is a major drawback from the standpoint of safety and the need for expensive equipment. In addition, in the hydrogenation step of aniline, intermediates such as enamines and imines are formed, which react additionally with aniline or cyclohexylamine to form N-phenylcyclohexylamine or dicyclohexylamine. It produces coupling by-products. For this reason, industrially, a large amount of anhydrous ammonia is generally used during the aniline hydrogenation step to suppress such a coupling reaction. However, the addition of anhydrous ammonia not only complicates the design of the reaction system, but also causes exhaust gas treatment and exhaust problems. For this reason, it is important to reduce the pressure without reducing the yield and selectivity during the conversion of aniline to cyclohexylamine.

US Pat. No. 4,384,142 (Monsanto)
Discloses a method for hydrogenating aniline to form cyclohexylamine in the presence of a noble metal Ru catalyst at a temperature of 160-180 ° C. and a hydrogen gas pressure of 20-50 atm. In this method, anhydrous ammonia is used as a coupling inhibitor.

[0005] German Patent No. 4207314 (BASF)
Discloses a method for hydrogenating aniline at 160 ° C. to form cyclohexylamine in the presence of a catalyst comprising a mixture of Ru, Pd and Mg and a BaCO ₃ support. Also in this method, anhydrous ammonia is used as a coupling inhibitor at a ratio of anhydrous ammonia: hydrogen gas = 2: 3.
After 24 hours of reaction, the resulting product has a cyclohexylamine: dicyclohexylamine ratio of 88.
6:11.

German Patent 38 24 822 (Bayer)
At a temperature of 200 ° C. and a hydrogen atmosphere at a high pressure of about 280 atm in the presence of Mn and Ce-modified Ru catalyst,
A method for hydrogenating aniline to form cyclohexylamine is disclosed. In this method, no coupling inhibitor is used. As a result, dicyclohexylamine (coupling by-product) has reached 58.3% of the total amount of the product.

German Patent No. 3801755 discloses a high-pressure process for the production of cyclohexylamine, which comprises:
The aniline is hydrogenated at a temperature of 109 ° C. and a hydrogen gas pressure of 280 atm in the presence of a Ru—Pd catalyst modified by Mn and Cr. The resulting product has a cyclohexylamine: dicyclohexylamine ratio of 91.1: 1.
It is reported to be 8.8.

JP-A-01-70466 (New Japan Science)
Discloses a method for hydrogenating aniline to form cycloheramine in the presence of 50% Ni / diatomaceous earth catalyst at a temperature of 190 ° C. and a hydrogen gas pressure of 7 atm. In this method, anhydrous ammonia is used as a coupling inhibitor at a ratio of ammonia: hydrogen gas = 1: 5, and the resulting product contains 75% cyclohexylamine.

[0009]

As described above, all of the prior art methods use a large amount of anhydrous ammonia as a coupling inhibitor or use a very high pressure (for example, 28 ° C.).
0 atm). The use of anhydrous ammonia as a coupling inhibitor complicates the reaction system and creates problems with exhaust gas treatment and emission. On the other hand, reactions at high pressures need to be carried out in high pressure resistant equipment, which is usually very expensive,
Also, the reaction under high pressure is a major drawback from the viewpoint of safety. In addition, most of these prior art processes suffer from unsatisfactory cyclohexylamine selectivity and the formation of large amounts of coupling by-products.

[0010] It is an object of the present invention to provide a method which can significantly improve the conversion of aniline compared to prior art methods using conventional hydrogenation catalysts such as ruthenium, palladium, Raney cobalt and Raney nickel. To provide cyclohexylamine from aniline in the presence of a catalyst selected from chromium-modified or thorium-modified cobalt boride.

Another object of the present invention is to provide a cyclohexylamine having a high selectivity without adding a coupling inhibitor, thereby simplifying a hydrogenation step and an exhaust gas treatment. It is an object of the present invention to provide a novel method for producing cyclohexylamine from aniline in the presence of a catalyst selected from chromium-modified or thorium-modified cobalt boride.

It is another object of the present invention to operate at pressures as low as 20 atm or less, thereby eliminating the need for expensive high pressure resistant equipment and minimizing factory safety concerns. Like you can
It is an object of the present invention to provide a novel method for producing cyclohexylamine from aniline in the presence of a catalyst selected from chromium-modified or thorium-modified cobalt boride.

[0013]

In order to solve the problems encountered in the prior art as described above, the present inventors have intensively studied these methods. As a result, the present inventors, when using a transition metal modified metal boride, without the presence of any coupling inhibitors, at a relatively low pressure,
It has been found that a hydrogenation reaction can be carried out. Also, a high conversion of aniline and a high selectivity of cyclohexylamine can be obtained. Using nickel boride modified with chromium, thorium or molybdenum as a catalyst under an atmosphere of hydrogen pressure lower than 20 atm and in the absence of a coupling inhibitor, it is possible to use certain catalysts such as ruthenium and palladium catalysts. It has been found that the conversion of aniline can be improved as compared with known catalysts. However, this conversion is comparable or slightly higher than that obtained with Raney nickel catalysts. Surprisingly, cobalt boride modified with chromium or thorium results in significantly higher aniline conversions, twice or more than that obtained with conventional Raney nickel catalysts, and also has a selectivity for cyclohexylamine over Raney nickel catalysts. Can provide a selectivity as high as (e.g., 90 mol%). Cobalt boride modified with molybdenum is not suitable for improving the conversion of aniline compared to Raney nickel catalyst, and is therefore not suitable.

[0014] Based on the above findings, the present inventors have found that in the presence of at least 0.6% by weight, based on the weight of aniline, of a chromium- or thorium-modified cobalt boride catalyst, 1
A novel process for the production of cyclohexylamine is proposed, comprising hydrogenating aniline at a temperature of 50-250 ° C. and a hydrogen pressure atmosphere of 1-20 atm.

The modified cobalt boride used in the present invention is prepared by modifying cobalt boride with an organic or inorganic salt of chromium or thorium. The amount of chromium in the chromium-modified cobalt boride is generally from 0.5 to 15%, preferably from 2 to 10%, more preferably from 2 to 8% by weight of the cobalt boride. The amount of thorium in the thorium-modified cobalt boride is generally from 0.1 to 20%, preferably from 2 to 15%, more preferably from 2 to 20% by weight of the cobalt boride.

In the process of the present invention, the amount of the modified cobalt boride used is generally at least 0.6% by weight, preferably 0.6-20% by weight, more preferably 2.0-2.0% by weight based on the weight of aniline. 15% by weight. If the amount of modified cobalt boride is less than 0.6% by weight, the conversion of aniline is
Usually not satisfactory. There is no specific upper limit for the amount of the modified cobalt boride used. The modified cobalt boride can be used repeatedly.

In the process of the present invention, the reaction temperature is generally from 150 to 250 ° C, preferably from 150 to 230 ° C, more preferably from 160 to 230 ° C. Reaction temperature is 150 ° C
If it is lower than this, satisfactory aniline conversion cannot be obtained. On the other hand, when the reaction temperature is higher than 250 ° C., the selectivity of cyclohexylamine is significantly reduced, resulting in an increase in coupling by-products.

In the production method of the present invention, the pressure of the hydrogen gas is generally 1 to 20 atm, preferably 3 to 20 atm.
If the hydrogen pressure is lower than 1 atm, satisfactory aniline conversion cannot be obtained. On the other hand, when the hydrogen pressure exceeds 20 atm, very expensive high-pressure resistant equipment is usually required,
It is also disadvantageous from the viewpoint of safety.

According to a preferred embodiment of the process of the present invention,
The hydrogenation reaction is carried out in the presence of a chromium or thorium-modified cobalt boride catalyst at a temperature of
It is performed under a pressure of 0 atm. In this embodiment, the modified cobalt boride is used in an amount of 2 to 15% by weight of the aniline weight. After completion of the reaction, the reaction mixture is distilled to obtain pure cyclohexylamine.

[0020]

Next, the present invention will be described in more detail with reference to Examples, Comparative Examples and Reference Examples, but the present invention is not limited to these.

Reference Example 1 Preparation of cobalt boride catalyst and nickel boride catalyst 20 mmol of cobalt acetate or nickel acetate was dissolved in 200 ml of deionized water, and 60 mmol of sodium borohydride (NaBH ₄ ) was dissolved in 60 ml of deionized water. Dissolved in. After complete dissolution, the aqueous solution of NaBH ₄ was slowly dropped into the cobalt acetate solution or the nickel acetate solution, whereby bubbles were generated and a black precipitate was formed.
After the bubbling has ceased, the precipitate is separated from the solution and washed successively with deionized water (3 times), 95% ethanol (2 times) and 99.5% ethanol (1 time),
Thus, a cobalt boride or nickel boride catalyst was obtained. These catalysts were washed with aniline, the starting material for the reaction, before addition to the reaction system.

Reference Example 2 Preparation of modified cobalt boride and modified nickel boride A modified cobalt boride and modified nickel boride were prepared in the same manner as in Reference Example 1. However, Cr, T
Modifiers selected from transition metal salts, such as h, Mo or Fe organic or inorganic salts, were added to the aqueous cobalt or nickel acetate solution prior to the addition of sodium borohydride to these solutions.

Example 1 800 g of aniline was placed in a 1 liter high pressure resistant reactor equipped with a gas gauge having a pressure gauge, a temperature controller, and a dispersion plate.
And 1.2 g (corresponding to 0.15% by weight of aniline weight) of cobalt boride catalyst modified with Cr or Th in the amounts listed in Table 1. Next, nitrogen gas was introduced into the reaction system to expel air from the reaction vessel. After the temperature of the reactor was raised to 180 ° C., hydrogen gas was introduced into the reactor to expel nitrogen gas, and then the reactor was pressurized to 5.5 atm. The reaction was continued for 10 hours while stirring at a stirring speed of 700 rpm and maintaining a constant hydrogen pressure of 5.5 atm. The obtained product was analyzed by gas chromatography, and the conversion of aniline and the selectivity of cyclohexylamine are shown in Table 1.

Comparative Example 1 The procedure of Example 1 was repeated, except that unmodified cobalt boride was used as the catalyst. Table 1 shows the conversion of aniline and the selectivity of cyclohexylamine.

Comparative Example 2 The procedure of Example 1 was repeated, except that 5% Ru / activated carbon was used as the catalyst. Table 1 shows the conversion of aniline and the selectivity of cyclohexylamine.

Comparative Example 3 The procedure of Example 1 was repeated except that Raney Cobalt (purchased from Nikko Rica, trade name: Raney Co Catalyst R-400) was used as the catalyst. Table 1 shows the conversion of aniline and the selectivity of cyclohexylamine.

Comparative Example 4 The procedure of Example 1 was repeated, except that unmodified nickel boride was used as the catalyst. Table 1 shows the conversion of aniline and the selectivity of cyclohexylamine.

Comparative Example 5 The procedure of Example 1 was repeated, except that nickel boride modified with various amounts of Cr, Th, Mo or Fe was used as the catalyst. Table 1 shows the conversion of aniline and the selectivity of cyclohexylamine.

Comparative Example 6 The procedure of Example 1 was repeated, except that cobalt boride modified with Mo was used as the catalyst. Table 1 shows the conversion of aniline and the selectivity of cyclohexylamine.

[Table 1]

Example 2 The procedure of Example 1 was repeated, except that 5% Cr-modified cobalt boride was used as the catalyst and the reaction temperature was varied as shown in Table 2. This example investigated the effect of reaction temperature on aniline conversion and cyclohexylamine selectivity. Table 2 shows the results.

[Table 2]

From Table 2, it was found that the conversion of aniline increased with increasing temperature. However, if the temperature is 250
At temperatures of up to ° C., the selectivity for cyclohexylamine was substantially reduced and the by-product dicyclohexylamine was significantly increased. Therefore, the reaction temperature is 25
It should not exceed 0 ° C.

Example 3 Except that 5% Cr-modified cobalt boride was used as the catalyst and the reaction pressure was varied as shown in Table 3.
The method of Example 1 was repeated. This example investigated the effect of reaction pressure on aniline conversion and clohexylamine selectivity. Table 3 shows the results.

[Table 3]

From Table 3, it was found that within the reaction pressure range of 1 to 20 atm, the conversion of aniline increased with increasing pressure and the selectivity of cyclohexylamine was maintained above 90 mol%.

Example 4 The procedure of Example 1 was repeated, except that 5% Th-modified cobalt boride was used as the catalyst and the amount of catalyst used was varied as shown in Table 4. This example investigated the effect of catalyst usage on aniline conversion and cyclohexylamine selectivity. Table 4 shows the results
Shown in The amount of the catalyst shown in Table 4 was shown by weight ratio to the weight of aniline.

[Table 4]

Example 5 Example 1 was repeated except that 5% Th-modified cobalt boride was used as the catalyst and this catalyst was used repeatedly.
Method was repeated. This example investigated whether the activity of the catalyst was reduced after repeated use.
Table 5 shows the results.

[Table 5]

From Table 5, it was found that repeated use of the catalyst did not substantially deteriorate its activity. The above embodiments are described for explaining the present invention,
It should not be understood as limiting the scope of the invention. Those skilled in the art can make various modifications and improvements based on the above description, and these modifications and improvements are
Without departing from the spirit and scope of the invention, it is encompassed by the technical scope of the invention.

Claims (7)

[Claims] 1. The method according to claim 1, wherein the weight of the aniline is at least 0.6.
Temperature of 150-250 ° C. and 1-20
A process for producing cyclohexylamine, which comprises hydrogenating aniline to form cyclohexylamine in a hydrogen atmosphere of atm. 2. The amount of chromium in the chromium-modified cobalt boride catalyst is 2 to 10% by weight of the weight of the cobalt boride;
The method according to claim 1, wherein the amount of thorium in the thorium-modified cobalt boride catalyst is 2 to 15% by weight based on the weight of the cobalt boride. 3. The method according to claim 1, wherein the amount of the modified cobalt boride catalyst used is 0.6 to 20% by weight based on the weight of aniline. 4. The method according to claim 1, wherein the amount of the modified cobalt boride catalyst used is 2 to 15% by weight based on the weight of aniline. 5. The method according to claim 1, wherein the hydrogenation reaction is performed in a hydrogen atmosphere of 3 to 20 atm. 6. The method according to claim 1, wherein the hydrogenation reaction is performed at a temperature of 150 to 230 ° C. 7. The hydrogenation reaction is carried out in the presence of a chromium-modified or thorium-modified cobalt boride catalyst in the range of 150 to 23.
The method according to claim 1, wherein the reaction is carried out at a temperature of 0 ° C and a hydrogen pressure atmosphere of 3 to 20 atm, and the amount of the cobalt boride catalyst used is 2 to 15% by weight of the weight of aniline.